In the past, in the rubber industry, the technique has been adopted of compounding carbon black as a reinforcing filler to reinforce the rubber, but when carbon black is compounded, there were the problems that the heat buildup of the rubber became higher and that, since the raw materials are derived from petroleum, the environmental load became larger. To solve these problems, in recent years, silica has been compounded as a filler (see Japanese Patent Publication (A) No. 05-51485). However, it is known that silica deteriorates the mixability because of easy agglomeration of silica particles due to the surface characteristics thereof. Therefore, it is known in the art that a silane coupling agent is combinedly used with silica when mixed with rubber with a good dispersability (see Japanese Patent Publication (A) No. 09-111044), but there is still room for improvement. In particular, a conventional silane coupling agent (e.g., mercaptosilane) greatly improves the dispersability of silica in the rubber. The resultant physical properties are also good, but there is the problem that there is a difficulty in the processability. As a technology for blocking the thiol parts of mercaptosilane, there is the technology of blocking with octanoic acid (U.S. Pat. No. 6,608,125). However, this largely decreases the reactivity of the mercapto groups. Although the octanoic acid is not detached at the vulcanization stage and the processing performance is good, this does not largely contribute to the physical properties after the vulcanization. Furthermore, there is the technology that a thiol compound and vinyl ethers are brought into contact to obtain a thiol compound derivative (see Japanese Patent Publication (A) No. 2003-055353). The inclusion of two or more thiol groups is preferable. When reacting with silica, the bound rubber structure around the silica becomes too hard and the resultant compound becomes unpreferable as a rubber composition for a tire.